The degradation of a device can be described by the degradation model in the accelerated tests. Because the degradation is closely related to the degradation mechanism, which reflects the intrinsic physical or chemical reactions, the degradation model can be established based on the temperature effect on the reaction rate and the change of reaction volume concentration in the physical/chemical reactions. Different degradation processes can be studied using the degradation model, including both the monotonic and nonmonotonic degradation processes. Moreover, the accelerated test is carried out for the GaN LED, figuring out the parameters for the degradation model, the ratio of different degradation processes, and the time constant.